To complement its current undergraduate research participant crew, the Dieckmann group is looking for several (preferentially MS&E) sophomores to participate in two different research projects beginning in Fall 2010. One of the projects deals with defects and transport in transition metal orthosilicates and the second one with the study of mixed glass former phenomena in certain glasses. Detailed project descriptions are given below.
If you should be interested in participating in one of the projects denoted above, please contact
228 Bard Hall
This is an ongoing NSF-supported research program. The project deals with point defects and the orientation-dependent transport of matter and charge in orthosilicates, i.e., ternary oxides of the type Me2SiO4. In the orthosilicates of interest Me is a transition metal, i.e., Co or Mn. Some investigations on defects and transport of matter and charge in orthosilicates with Me = Fe have been performed in the Dieckmann lab some time ago. The results from this earlier work have revealed a very significant anisotropy in the diffusion of iron and in the electrical conduction. The more recent research is to find out whether this anisotropy is a common feature of orthosilicates with Me being transition metals or not and how the anisotropies change with the type of Me. The work performed includes the growth of orthosilicate single crystals with different orientation and different composition, i.e., with Me = Co or Mn, measurements of the variation of the oxygen content of Me2SiO4+δ with the oxygen partial pressure at different temperatures and measurements of tracer diffusion coefficients for Me (= Co or Mn, respectively) for different crystal orientations. At present, the focus is on an orthosilicate with Me = Mn which is called tephroite.
Currently, several undergraduate students are participating in this program. They are involved in the preparation of manganese orthosilicate samples (powder synthesis via both a traditional ceramic route and a sol-gel synthesis route, making polycrystalline feed rods for single crystal growth, single crystal growth by the floating zone technique, cutting and grinding of single crystal samples, etc.), and the characterization of samples (density, microstructure, phase purity, crystal orientation, dislocation density, etc.). Measurements of cation tracer diffusion coefficients as a function of temperature and oxygen activity in cobalt orthosilicate samples have been performed. Measurements of cation tracer diffusion coefficients are planned to begin soon for manganese orthosilicate samples. Undergraduate students are expected to perform a very significant fraction of these experiments and also to participate in sample preparation and characterization.
The NSF-supported project “Study of Mixed Glass
Former Phenomena in Materials” is part of an international collaborative
educational and research program within the NSF-DMR sponsored Materials World
Network. Collaborators in the U.S. are from Iowa State University (Steve W.
Martin) and from Central Michigan University (Valeri Petkov). Collaborators in
The project at Cornell deals with the tracer diffusion of cations in the type of glasses denoted above. The glasses investigated at Cornell were prepared by Corning Inc. The Dieckmann group has measured sodium tracer diffusion coefficients as a function of temperature, glass composition in glasses of the type (Na2O)0.2·[(BO1.5)x(SiO2)1-x]0.8 using the radioactive isotope Na-22. The observed temperature and composition dependencies are intended to be linked to structural observations made by collaborating groups. Glasses of other compositions to be investigated in the future are currently under discussion.
Since water incorporated into oxide glasses can significantly influence many glass properties, the Dieckmann group also investigates the uptake of water by oxide glasses and the influence of water taken up by such glasses during diffusion-annealing or during pre-annealing on the tracer diffusion of cations. The analytical being used for detecting OH-groups generated due to an uptake of water by oxide glasses is an FT-IR spectrometer with a microscope attached to it.
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